I think it doesn't matter. In Betcoin.ag rules it's clearly written that they don't accept players from USA, so, your friends break their rules and they are risking to get their account closed.
As far as I know, Betcoin usually has no issues with USA players which is why I recommended it though he can always sign up on the popular FIAT sites which I recommended earlier if he is still hesitant in this case.
I have checked your list and almost all sportsbooks, except Bovada isn't known for me. I'm not sure, is it good idea to play in not well known sportsbook without solid reputation. Before joining it, I advice OP to make research about it.
Most of the books are actually very popular around the world though they are primarily FIAT only and they accept crypto as a payment method. Majority of these sites require KYC initially.